Highlights by GreenFacts of the executive summary of the Report “Turn down the heat ~ 4°C “
A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics http://climatechange.worldbank.org/content/climate-change-report-warns-dramatically-warmer-world-century
The conclusions of the report in a glance
This report spells out what the world would be like if it warmed by 4 degrees Celsius, which is what scientists are nearly unanimously predicting by the end of the century, without serious policy changes.
It is a stark reminder that climate change affects everything. The solutions don’t lie only in climate finance or climate projects. The solutions lie in effective risk management and ensuring all our work, all our thinking, is designed with the threat of a 4°C degree world in mind.
The President of the World Bank Group, Dr. Jim Yong Kim, is very clear in its foreword of the report : The lack of action on climate change not only risks putting prosperity out of reach of millions of people in the developing world, it threatens to roll back decades of sustainable development. The scenarios evaluating the consequences of an increase of the global earth temperature of 4°C are indeed devastating:
- the inundation of coastal cities;
- increasing risks for food production potentially leading to higher malnutrition rates; many dry regions becoming dryer, wet regions wetter;
- unprecedented heat waves in many regions, especially in the tropics;
- substantially exacerbated water scarcity in many regions;
- increased frequency of high-intensity tropical cyclones;
- irreversible loss of biodiversity, including coral reef systems.
The science , he says, is unequivocal that humans are the cause of global warming, and major changes are already being observed: global mean warming is 0.8°C above pre industrial levels; oceans have warmed by 0.09°C since the 1950s and are acidifying. Sea levels rose by about 20 cm since pre-industrial times and are now rising at 3.2 cm per decade; an exceptional number of extreme heat waves occurred in the last decade; major food crop growing areas are increasingly affected by drought.
Dr Kim underlines that the World Bank is well aware of the uncertainty that surrounds these scenarios and that different scholars and studies sometimes disagree on the degree of risk. But, he adds,the fact that such scenarios cannot be discarded is sufficient to jus tify strengthening current climate change policies.
This why the global conclusion of the report is that the projected 4°C warming simply must not be allowed to occur—the heat must be turned down. Only early, cooperative, international actions can make that happen.
The Highlights of the report in 13 Questions and 13 Answers
1. What does this report provide about climate change?This report provides a snapshot of recent scientific literature and new analyses of likely impacts and risks that would be associated with a 4° Celsius warming within this century. It is a rigorous attempt to outline a range of risks, focusing on developing countries and especially the poor while recognizing that developed countries are also vulnerable and at serious risk of major damages from climate change. It highlights that a series of recent extreme events worldwide continue to highlight the vulnerability of not only the developing world but even wealthy industrialized countries.
2. Is it still possible to avoid a global temperature increase of 4°C? With action, a 4°C world can be avoided and we can likely hold warming below 2°C.Numerous studies show that there are technically and economically feasible emissions pathways to hold warming likely below 2°C. Thus the level of impacts that developing countries and the rest of the world experience will be a result of government, private sector, and civil society decisions and choices, including, unfortunately, inaction.
The global community has committed itself to holding warming below 2°C to prevent “dangerous” climate change but the sum total of current policies—in place and pledged—will very likely lead to warming far in excess of these levels. Indeed, present emission trends put the world plausibly on a path toward 4°C warming within the century.
3. What if this 4°C increase is not avoided? A world in which warming reaches 4°C above preindustrial levels (hereafter referred to as a 4°C world), would be one of unprecedented heat waves, severe drought, and major floods in many regions, with serious impacts on human systems, ecosystems, and associated services.
By comparison, a global mean temperature increase of 4°C approaches the difference between temperatures today and those of the last ice age, when much of central Europe and the northern United States were covered with kilometers of ice and this magnitude of climate change—human induced—is occurring over a century, not millennia.
If action are not fully implemented, a warming of 4°C could occur as early as the 2060s. Such a warming level by 2100 would not be the end point: a further warming to levels over 6°C would likely occur over the following centuries.
Small Island Developing states (SIDS) and Least Developed Countries (LDCs) have identified global warming of 1.5°C as warming above which there would be serious threats to their own development and, in some cases, survival. The distribution of impacts is likely to be inherently unequal and tilted against many of the world’s poorest regions, which have the least economic, institutional, scientific, and technical capacity to cope and adapt. For example:
• Even though absolute warming will be largest in high latitudes, the warming that will occur in the tropics is larger when compared to the historical range of temperature and extremes to which human and natural ecosystems have adapted and coped. The projected emergence of unprecedented high-temperature extremes in the tropics will consequently lead to significantly larger impacts on agriculture and ecosystems.
• Sea-level rise is likely to be 15 to 20 percent larger in the tropics than the global mean.
• Increases in tropical cyclone intensity are likely to be felt disproportionately in low-latitude regions.
• Increasing aridity and drought are likely to increase substantially in many developing country regions located in tropical and subtropical areas.
4. How reliable are the scenario’s build to support such an increase of the global temperature and its consequences? Uncertainties remain in projecting the extent of both climate change and its impacts.The impacts of the extreme heat waves projected for a 4°C world have not been evaluated, but they could be expected to vastly exceed the consequences experienced to date (heat-related deaths, forest fires, harvest losses) and potentially exceed the adaptive capacities of many societies and natural systems. The authors take a risk-based approach in which risk is defined as impact multiplied by probability: an event with low probability can still pose a high risk if it implies serious consequences. Although it is often difficult to make comparisons across individual assessments, this report identifies a number of extremely severe risks for vital human support systems.
Large-scale and disruptive changes in the Earth system are generally not included in modeling exercises, and rarely in impact assessments. As global warming approaches and exceeds 2°C, the risk of crossing thresholds of nonlinear tipping elements in the Earth system, with abrupt climate change impacts and unprecedented high-temperature climate regimes, increases. Examples include the disintegration of the West Antarctic ice sheet leading to more rapid sea-level rise than projected in this analysis.
There might also be nonlinear responses within particular economic sectors to high levels of global warming. For example, nonlinear temperature effects on crops are likely to be extremely relevant as the world warms to 2°C and above. However, most of our current crop models do not yet fully account for this effect, or for the potential increased ranges of variability (for example, extreme temperatures, new invading pests and diseases, abrupt shifts in critical climate factors that have large impacts on yields and/or quality of grains).
Projections of damage costs for climate change impacts typically assess the costs of local damages, including infrastructure, and do not provide an adequate consideration of cascade effects (for example, value-added chains and supply networks) at national and regional scales. Thus, given that uncertainty remains about the full nature and scale of impacts, there is also no certainty that adaptation to a 4°C temperature increase is possible. A “4°C world” is likely to be one in which communities, cities and countries would experience severe disruptions, damage, and dislocation, with many of these risks spread unequally. It is likely that the poor will suffer most and the global community could become more fractured, and unequal than today.
5. What are the main Impacts already observed on the climate system? Seven main unequivocal effects of greenhouse gas emissions already observed have continued to intensify, more or less unabated:
- The concentration of the main greenhouse gas, carbon dioxide (CO2), has continued to increase from its preindustrial concentration to over 391 ppm in September 2012, with the rate of rise now at 1.8 ppm per year;
- The present CO2 concentration is higher than paleoclimatic and geologic evidence indicates has occurred at any time in the last 15 million years;
- Global mean temperature is now about 0.8°C above preindustrial levels and continue to increase;
- The global oceans have continued to warm, with about 90 percent of the excess heat energy trapped by the increased greenhouse gas concentrations since 1955 stored in the oceans as heat.
- In the meantime, the rate of loss of ice has more than tripled since the 1993–2003 period.
- The average increase in sea levels has been about 15 to 20 centimeters around the world over the 20th century and now increases by about 3.2 cm per decade. Should this rate remain unchanged, this would mean over 30 cm of additional sea-level rise in the 21st century. The accelerating loss of ice from the Greenland and Antarctic ice sheets could add substantially to sea-level rise in the future, about 15 cm by the end of the 21st century.
- An increased frequency and intensity of heat waves is observed with, in some climatic regions, increased in intensity of extreme precipitation and drought . Observations indicate a tenfold increase in the surface area of the planet experiencing extreme heat since the 1950s.As for Arctic sea ice, it reached a record minimum in September 2012, halving the area of ice covering the Arctic Ocean in summer.
6. What are the further climate change expected with a 4°C temperature increase? The largest warming will occur over land and range from 4°C to 10°C. Increases of 6°C or more in average monthly summer temperatures would be expected in large regions of the world, including the Mediterranean, North Africa, the Middle East. Almost all summer months are likely to be warmer than the most extreme heat waves presently experienced and, for example, the warmest July in the Mediterranean region could be 9°C warmer than today’s warmest July.
Recent extreme heat waves such as in Russia in 2010 are likely to become the new normal summer in a 4°C world. Tropical South America, central Africa, and all tropical islands in the Pacific are likely to regularly experience heat waves of unprecedented magnitude and duration. In this new high-temperature climate regime, the coolest months are likely to be substantially warmer than the warmest months at the end of the 20th century.
7. What are the effects expected on sea levels and and their consequences? Sea-level rise will vary regionally; it is projected to be up to 20 percent higher in the tropics and below average at higher latitudes. Only 10 cities account for two-thirds of the total exposure to extreme floods. Highly vulnerable cities are to be found in Mozambique, Madagascar, Mexico, Venezuela, India, Bangladesh, Indonesia, the Philippines, and Vietnam. Small island states and river delta regions, rising sea levels are likely to have far ranging adverse consequences, especially when combined with the projected increased intensity of tropical cyclones, loss of protective reefs due to temperature increases and ocean acidification. Changes in wind and ocean currents due to global warming and other factors will also affect regional sea-level rise, as will patterns of ocean heat uptake and warming.
Warming of 4°C will likely lead to a sea-level rise of 0.5 to 1 meter, and possibly more, by 2100, with several meters more to be realized in the coming centuries. Sea-level rise would likely be limited to below 2 meters only if warming were kept to well below 1.5°C. Even if global warming is limited to 2°C, global mean sea level could continue to rise, with some estimates ranging between 1.5 and 4 meters above present-day levels by the year 2300.
8. What are the effects expected from rising temperature on corals reefs and why are these a concern? One of the most serious consequences of rising carbon dioxide concentration in the atmosphere occurs when it dissolves in the ocean and results in acidification. A substantial increase in ocean acidity has been observed since preindustrial times. A warming of 4°C or more by 2100 would correspond to an increase of about 150 percent in acidity of the ocean , a change which appears to be unparalleled in Earth’s history. Evidence is already emerging of the adverse consequences of acidification for marine organisms and ecosystems, combined with the effects of warming, overfishing, and habitat destruction.
The combination of thermally induced bleaching events, ocean acidification, and sea-level rise threatens large fractions of coral reefs even at 1.5°C global warming. Coral reefs in particular are indeed acutely sensitive to changes in water temperatures, ocean pH, and intensity and frequency of tropical cyclones. Reefs provide protection against coastal floods, storm surges, and wave damage as well as nursery grounds and habitat for many fish species. By the time the warming is of about 2.4°C in the 2060s, it is likely that coral reefs in many areas would start to dissolve.
9. What are the risks expected to water resources if the global mean temperature raises by 4°C? With extremes of temperature, heat waves, rainfall, and drought are projected to increase with warming; increasing vulnerability to heat and drought stress will likely lead to increased mortality and species extinction.
Although the most adverse impacts on water availability are likely to occur in association with growing water demand as the world population increases, some estimates indicate that a 4°C warming would significantly exacerbate existing water scarcity in many regions, particularly northern and eastern Africa, the Middle East, and South Asia, while additional countries in Africa would be newly confronted with water scarcity on a national scale due to population growth.
• Drier conditions are projected for southern Europe, Africa (except some areas in the northeast), large parts of North America and South America, and southern Australia, among others.
• Wetter conditions are projected in particular for the northern high latitudes—that is, northern North America, northern Europe, and Siberia—and in some monsoon regions. Some regions may experience reduced water stress compared to a case without climate change.
• Changes to the hydrological cycles associated with severe risks in some regions, such as flooding and drought, which may increase significantly even if annual averages change little.
With a 2°C temperature increase :
- River basins dominated by a monsoon regime, such as the Ganges and Nile, are particularly vulnerable to changes in the seasonality of runoff, which may have large and adverse effects on water availability.
- Mean annual runoff is projected to decrease by 20 to 40 percent in the Danube, Mississippi, Amazon, and Murray Darling river basins, but increase by roughly 20 percent in both the Nile and the Ganges basins.
All these changes approximately double in magnitude with a 4°C temperature increase.
10. What are the risks expected to ecosystems if the global mean temperature raises by 4°C ? Recent research suggests that large-scale loss of biodiversity is likely to occur with a temperture increase of 4°C, with climate change and high CO2 concentration driving a transition of the Earth´s ecosystems into a state unknown in human experience. In fact, climate change seems likely to become the dominant driver of ecosystem shifts, surpassing habitat destruction as the greatest threat to biodiversity.
Ecosystems will be affected by more frequent extreme weather events, such as forest loss due to droughts and wildfire exacerbated by land use and agricultural expansion. In Amazonia, forest fires could as much as double by 2050 with warming of approximately 1.5°C to 2°C above preindustrial levels. Changes would be expected to be even more severe in a 4°C world.
Ecosystem damage would be expected to dramatically reduce the provision of ecosystem services on which society depends (for example, fisheries and protection of coastline—afforded by coral reefs and mangroves).
11. What are the effects expected on food availability? In 2007, the IPCC projected that global food production would increase for local average temperature rise in the range of 1°C to 3°C, and may decrease beyond these temperatures but new results suggest instead a rapidly rising risk of crop yield reductions as the world warms and observations indicate a significant risk of high-temperature thresholds being crossed that could substantially undermine food security globally with a 4°C temperaure increase.
Large negative effects have been observed at high and extreme temperatures in several regions including India, Africa, the United States, and Australia. For example, significant nonlinear effects have been observed in the United States for local daily temperatures increasing to 29°C for corn and 30°C for soybeans. These new results
Compounding these risks is the adverse effect of projected sea level rise on agriculture in important low-lying delta areas, such as in Bangladesh, Egypt, Vietnam, and parts of the African coast. Sea-level rise would likely impact many mid-latitude coastal areas and increase seawater penetration into coastal aquifers used for irrigation of coastal plains. Further risks are posed by the likelihood of increased drought in mid-latitude regions and increased flooding at higher latitudes.
12. What are the effects expected to occur to human health and wealth? Large-scale extreme events, such as major floods that interfere with food production, could induce nutritional deficits and the increased incidence of epidemic diseases. Flooding can introduce contaminants and diseases into healthy water supplies and increase the incidence of diarrheal and respiratory illnesses. The effects of climate change on agricultural production may exacerbate under-nutrition and malnutrition in many regions—already major contributors to child mortality in developing countries.
Whilst economic growth is projected to significantly reduce childhood stunting, climate change is projected to reverse these gains in a number of regions with warming of 2°C to 2.5°C, especially in Sub-Saharan Africa and South Asia, and this is likely to get worse at 4°C. Despite significant efforts to improve health services (for example, improved medical care, vaccination development, surveillance programs), significant additional impacts on poverty levels and human health are expected. Changes in temperature, precipitation rates, and humidity influence vector-borne diseases (for example, malaria and dengue fever) as well as hantaviruses, leishmaniasis, Lyme disease, and schistosomiasis.
Further health impacts of climate change could include injuries and deaths due to extreme weather events. Heat-amplified levels of smog could exacerbate respiratory disorders and heart and blood vessel diseases, while in some regions climate change–induced increases in concentrations of aeroallergens (pollens, spores) could amplify rates of allergic respiratory disorders.
13. What are the risks of disruptions and displacements expected with a global temperature increase of 4°C? Economic growth and population increases over the 21st century will be increasing stresses and demands on a planetary ecosystem already approaching critical limits and boundaries. The resilience of many natural and managed ecosystems is likely to be undermined by these pressures and the projected consequences of climate change.
The projected impacts on water availability, ecosystems, agriculture, and human health could lead to large-scale displacement of populations and have adverse consequences for human security and economic and trade systems.
Projections of damage costs for climate change impacts do not provide an adequate consideration of cascade effects (for example, value-added chains and supply networks) at national and regional scales. However, in an increasingly globalized world that experiences further specialization in production systems, and thus higher dependency on infrastructure to deliver produced goods, damages to infrastructure systems can lead to substantial indirect impacts. Seaports are an example of an initial point where a breakdown or substantial disruption in infrastructure facilities could trigger impacts that reach far beyond the particular location of the loss but their cumulative and interacting effects are not well understood.
With pressures increasing as warming progresses toward 4°C and combining with nonclimate–related social, economic, and population stresses, the risk of crossing critical social system thresholds will grow. At such thresholds existing institutions that would have supported adaptation actions would likely become much less effective or even collapse. One example is a risk that sea-level rise in atoll countries exceeds the capabilities of controlled, adaptive migration, resulting in the need for complete abandonment of an island or region. Similarly, stresses on human health, such as heat waves, malnutrition, and decreasing quality of drinking water due to seawater intrusion, have the potential to overburden health-care systems to a point where adaptation is no longer possible, and dislocation is forced.
Reference “Turn down the heat ~ 4°C “ A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics This work is a product of the staff of The World Bank with external contributions.
The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent.
The report was commissioned by the World Bank’s Global Expert Team for Climate Change Adaptation,and has been written by a team from the Potsdam Institute for Climate Impact Research and Climate Analytics.
Because The World Bank encourages dissemination of its knowledge, this work may be reproduced, in whole or in part, for noncommercial purposes as long as full attribution to this work is given.
© 2012 of the original report: International Bank for Reconstruction and Development / The World Bank Washington DC 20433. www.worldbank.org
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